OMAA- YSSY is a 13hr flight. Steps are normal but Simbrief planned for FL330 in my inibuilds A35K with a step down after a few hundred miles to FL310 for the next few thousand miles.
The aircraft couldn’t climb past FL310 initially. I can’t find any reason for the step down. In real life acft on this route regularly start at FL310
Basically, up until the first custom step climb at LOTAV, SimBrief selected an altitude automatically (FL330 in this case at your planned weight). However, after LOTAV, it began following your custom altitudes for the remainder of the route.
If you prefer SimBrief to automatically calculate all step climbs, you will need to remove them from your route when pasting into SimBrief.
If you instead want to force SimBrief to stay at FL310 up until your first custom step climb, enter “31000” into the “Altitude” parameter.